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Cilia and Ciliary Movements



Cilia

  • Cilia are small, slender, and hair-like structures on the surface of cells.

Types

  • Nonmotile Cilia

    • Cannot move on their own.

    • Play sensory role

  • Motile Cilia

    • Can move on their own → their movement generates flow in the fluid on the surface of the cell.

Structure of a Cilium

Basal Body

  • Cilium arises from its own basal body.

  • Basal body is a centriole immediately beneath the cell membrane

Axoneme

  • Made up of microtubules

  • 2 complete microtubules at the center

  • 9 pairs of microtubules at the periphery.

  • Each peripheral pair is connected to its neighboring pairs by dynein arms.

Cell Membrane

  • Covers the Axoneme

Ciliary Movement

  • Cilia move in a whip-like motion.

Forward Stroke

  • is a rapid forward thrusting movement.

  • Moves the fluid on the surface in forward direction.

Backward Stroke

  • is a slow dragging movement in backward direction.

  • Produces minimal effect movement of fluid.

Mechanism of Ciliary Movement

  • Dynein arm of peripheral pairs of tubules crawls over its neighbor pair → As all the pairs are fixed at the base, the crawling results in bending of the cilia.

  • Dynein arm uses energy from ATP to produce this movement.

Importance of Ciliary Movement

In Respiratory Tract

  • Ciliary movement on the epithelial cell of the airway generates flow in the mucous → move the inhaled foreign particles and pathogens in nose and lower respiratory tract to pharynx → swallowed → respiratory tract is cleared.

In Fallopian Tube

  • Move the ovum from ovary to uterus.

 

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